Term
|
Definition
| a special dispersion-strengthening heat treatment. by solution treatment, quenching, and aging, a coherent precipitate forms that provides a substantial strengthening effect. (also known as precipitation hardening) |
|
|
Term
|
Definition
| reheating a solution-treated and quenched alloy to a temperature below the solvus in order to provide the thermal energy required for a precipitate to form |
|
|
Term
|
Definition
| when the amount of the transformation depends only on the temperature, not on the time (same as martensitic transformation or displacive transformation). |
|
|
Term
|
Definition
| a two-phase microconstituent, containing ferrite and cementite, that forms in steels that are isothermally transformed at relatively low temperatures |
|
|
Term
|
Definition
| the hard, brittle, ceramic-like compound Fe3C that, when properly dispersed, provides the strengthening in steels |
|
|
Term
|
Definition
| a precipitate whose crystal structure and atomic arrangement have a continuous relationsip with the matrix from which the precipitate is formed. the coherent precipitate provides excellent disruption of the atomic arrangement in the matrix and provides excellent strengthening |
|
|
Term
|
Definition
| a precipitate whose crystal structure and atomic arrangement have a continuous relationsip with the matrix from which the precipitate is formed. the coherent precipitate provides excellent disruption of the atomic arrangement in the matrix and provides excellent strengthening |
|
|
Term
|
Definition
| the name given to the BCC crystal structure of iron that can occur as (alpha) or (delta). this is not to be confused with ceramic ferrites which are magnetic materials |
|
|
Term
| Guinier-Preston (GP) zones |
|
Definition
| tiny clusters of atoms that precipitate from the matrix in the early stages of the age-hardening process. although the GP zones are coherent with the matrix, they are too small to provide optimum strengthening. |
|
|
Term
|
Definition
| a metastable phase formed in steel and other materials by a diffusionless, a thermal transformation |
|
|
Term
| martensite transformation |
|
Definition
| a phase transformation that occurs without diffusion. same a thermal or displacive transformation. these occur in steels, Ni-Ti and many ceramic materials. |
|
|
Term
|
Definition
| when a coherent precipitate forms from a solution-treated and quenched age-hardenable alloy at room temperature, providing optimum strengthening |
|
|
Term
|
Definition
| a two-phase lamellar microstituent, containing ferrite and cementite, that forms in steels cooled in a normal fashion or isothermally transformed at relatively high temperatures |
|
|
Term
|
Definition
| the first step in the age-hardening heat treatment. the alloy is heated above the solvus temperature to dissolve any second phase and to produce a homogeneous single-phase structure. |
|
|
Term
| supersaturated solid solution |
|
Definition
| the solid solution formed when a material is rapidly cooled from a high-temperature single-phase region to a low temperature two-phase region without the second phase precipitating. because the quenched phase contains more alloying element than the solubility limit, it is supersaturated in that element |
|
|
Term
|
Definition
| a low-temperature heat treatment used to reduce the hardness of martensite by permitting the martensite to begin to decompose to the equilibrium phases. this leads to increased toughness. |
|
|
Term
| time-temperature-transformation (TTT) diagram |
|
Definition
| the TTT diagram describes the time required at any temperature for a phase transformation to begin and end. the TTT diagram assumes that the temperature is constant during the transformation |
|
|
